Database Migration is moving applications, cron jobs, all components and data transfer from legacy database software system to another new database software system. Here database software system in the sense Data warehouse or Hadoop or any other system which can handle the existing functionality and handle the data without any performance issues. A plenty of database testing will be involved especially in data migration projects. Here are the varieties of data migration case studies like Migration of DW to Hadoop, Migration of ODS (Operational Data Store)to Pentaho or any other ETL tool etc. Any of the data migration or replacing ETL Tool with another ETL tool we should have the parallel system in the process, so that the data comparison should be pretty some easy going process.

As we know ETL stands for Extract, Transform and Load. Generally ETL things will comes into picture with respect the data i.e., OLAP data. So many paid and free ware tools available in the market like Informatica, Datastage, Oracle data Integrator and Pentaho etc. In a simple manner what we are testing here is data from source modified based on some conditions and will be inserted into target tables.

Source: The source may be any format like flat files, tables, xml files etc.,These source data is generated from other jobs or other applications, we don't bother how the data is coming or from where the data is coming, here our concentration should be the source data should be inserted into one or two tables and one or more records. If you take in informatica the jobs are called workflows, it might be hourly workflows which will run hourly, or daily workflows which runs once in a day based on the design.